How can I get better battery life out of my game boy micro?

[actualkoifish]

I've been using my game boy micro a lot recently, and have noticed the battery life is not very good. I have a new mahko 750mah battery and I mostly play NES games on the pocketnes emulator, running off the SZ Flash 4 mini SD card version. I have noticed that I only get maybe 5 hours in this way. I recall getting better life back when it was new, though admittedly that's almost 15 years ago now and so I don't really remember. Just feels like I should be getting more, especially now that I have the new, extended battery.
What are some things that can improve my battery life? Would a new flash cart be more efficient? Or maybe I could burn a permanent cart with NES games and it would run more efficiently that way? I already play with lowest brightness and sound off, so not sure I can do much more there.

 

[FAST6191]

Most third party batteries are lies and unpleasantness. Some flash carts gobble a bit more than some commercial games but the EZ4 miniSD should not be too bad.

The battery being old might not help (they don't tend to make new ones so it too likely sat on the shelf for a while at this point).

Anyway not much I can say for this -- other than things like lower screen brightness (not really an option), volume I guess (fractional difference and probably lost in the noise), attach a battery bank, get another battery and do a swap or parallel battery, maybe consider one of the truly low power flash carts... those at the easy steps. After that we get silly and start contemplating hardware changes. The "sensible" ones are also going to be trick for a GBM form factor as well -- fine for an original GBA and even probably SP but for a tiny Micro... I am seeing some problems with that approach.